As I said in the NCAA forum, this isn't going to happen unless the owners committee can convince the NFLPA that it's a good idea, and there isn't a huge chance of that happening.
There are FAR too many NFL players that don't wear thigh or knee pads now to make this major change. The ship sailed. Rich McKay saying that the owners can implement this without player approval is a pipe dream, a PR ploy.
And until the NFL mandates that players use the best helmets (which 80% currently do NOT do), anything like requiring thigh pads is putting lipstick on a pig. The number of injuries that come from not wearing thigh or knee pads is next to zero. But the concussion issue is the elephant in the room.